1. Field of the Invention
The present invention relates to a tape unit for use in recording by a thermal recording system and, more particularly, to an end tape for connecting a thermal recording material for forming a printed image and a core for winding the thermal recording material.
2. Description of the Related Art
A thermal recording material and a thermal recording system using it are easier to handle than any other recording materials and recording systems using them now in practical application. Further, a thermal recording device to which the thermal recording material and the thermal recording system are applied is relatively inexpensive. Accordingly, the thermal recording material and the thermal recording system are widely used for outputting in a computer, facsimile, recorder, etc.
The thermal recording material is generally classified into an ink ribbon for use in a thermal transfer system for transferring an original image to a recording medium by using a thermal print head (thermal head) and a heat-sensitive recording sheet such as a heat-sensitive paper or a heat-sensitive plastic film on which a printed image is to be directly recorded by heat from the thermal head.
In the thermal transfer system typically using such an ink ribbon, the ink ribbon having a given width and a length of several meters is wound around a reel to form a roll, and this roll is set in a printing device for practical use. In a printing operation, the roll is suitably unwound to feed the ink ribbon to the thermal head, and heat from the thermal head is applied to the ink ribbon from the side opposite to an ink coated surface of the ink ribbon according to a desired input image of characters, thereby forming a printed image on the recording medium facing the ink coated surface of the ink ribbon. Such a printing device using an ink ribbon is disclosed as a tape writer in U.S. Pat. No. 4,927,278 (Japanese Utility Model Publication No. Hei 4-32290).
The heat-sensitive recording sheet inclusive of the heat-sensitive paper and the heat-sensitive plastic film can also form a printed image by using a similar printing device as mentioned above with the exception that no recording medium is needed.
The thermal recording material is gradually consumed to an end as the printing operation proceeds. Until the thermal recording material comes to an end during the printing operation, there occurs no problem in printing. However, at the time the thermal recording material is fully consumed, the heat from the thermal head is concentrated at one position to bring about an adverse effect on any members surrounding the thermal head.
More specifically, when the ink ribbon is not connected to the reel, the ending of the ink ribbon results in separation of the ink ribbon from the reel. Accordingly, the free ink ribbon is fed to pass between the thermal head and a platen opposed to the thermal head. Thereafter, the ink ribbon is absent between the thermal head and the platen. If an operator does not know the ending of the ink ribbon and continues the printing, the thermal head comes into direct contact with the platen and continues to apply heat to the platen. As a result, a contact portion of the platen contacting the thermal head becomes very high in temperature and thus damaged or deformed, causing a change in printing conditions. In this event, the platen must be replaced in order to obtain a good print quality again. Further, the thermal head itself is possibly damaged.
Disclosed in U.S. Pat. No. 4,983,058 (Japanese Utility Model Publication No. Hei 4-34048) is a tape cassette storing a printing tape and an ink ribbon for thermal transferring an original image to the printing tape. That is, the original image such as characters are printed on the printing tape through the ink ribbon by using a thermal head. An end tape is attached to a trailing end of the printing tape in order that an operator can confirm the ending of the printing tape. When the end tape is visually perceived by the operator, the ending of the printing tape is confirmed by the operator to stop printing on the printing tape. Even if the operator fails to visually perceive the end tape and continues the printing on the printing tape after the ending of the printing tape, there is no possibility that the end tape may be melted by the heat from the thermal head because the ink ribbon is present between the end tape and the thermal head to absorb the heat from the thermal head. However, in case the ink ribbon and the reel are connected together by using an end tape similar to that described in U.S. Pat. No. 4,983,058 mentioned above, the end tape is fed from the reel after the ink ribbon is fully used for printing. Immediately thereafter, the feed of the end tape is stopped to cause a phenomenon that the thermal head continues to heat the end tape at its same position. In this event, the conventional end tape is possibly melted by the heat from the thermal head to stick to the thermal head. Such a deposition of the melted end tape on the thermal head disables transmission of the heat from the thermal head to the thermal recording material in the next printing operation, thus rendering printing impossible. It is very difficult to remove such a deposition stuck to the thermal head, and an organic solvent or the like must be used to clean the thermal head, causing an adverse effect on any members surrounding the thermal head. In some cases, the end tape is possibly cut to be entangled within the tape cassette or the printing device. Further, it is apparent that this problem also occurs in case the thermal recording material is directly connected to the reel without using the end tape.
Although this problem may be eliminated by providing a mechanism for sensing the ending of the thermal recording material in the printing device, such a mechanism is very expensive and complicated in structure, thus impeding easy provision for the mechanism in the printing device.